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This invention relates to vinyl copolymer emulsions and to their use as additives for paints and coatings. More particularly, it relates to a highly storage stable vinyl copolymer emulsion that is capable of forming strongly water repellent and highly water resistant films and coatings. The invention also relates to a paint or coating additive that is highly compatible with paints and coating compositions and that includes the emulsion.
Japanese Patent Application Publication 5-9248 (9,248/1993) and Japanese Patent Application Publication 1-284513 (284,513/1989) disclose silicone grafted vinyl copolymer emulsions with improved water repellency, water resistance, and lubricity of vinyl polymer emulsions. These silicone grafted vinyl copolymer emulsions are produced by emulsion polymerization of vinyl monomers with straight chain or partially branched silicone macromonomers bearing radically polymerizable functional groups. One problem, however, is the presence of residual unpolymerized silicone macromonomer after completion of the reaction. This is due to the inadequate reactivity of the silicone macromonomer with the vinyl monomer during emulsion polymerization. When the resulting vinyl copolymer emulsion is coated on a substrate, the unpolymerized silicone macromonomer bleeds out onto the surface of the coating. This impairs its compatibility with other materials, diminishes its adherence with various substrates, and reduces printability. In addition, the silicone grafted vinyl copolymer emulsions have an inadequate storage stability, while coatings produced from these compositions exhibit an inadequate water repellency and an inadequate water resistance. Finally, these silicone grafted vinyl copolymer emulsions suffer from the problem that they exhibit an unsatisfactory compatibility with waterborne coating compositions when employed as modifiers of waterborne coatings.
Therefore, it is an object of this invention is to provide a highly storage stable vinyl copolymer emulsion that can form strongly water repellent and highly water resistant films and coatings. Another object is to provide paint or coating additives that are highly compatible with paints and coatings. These and other features of the invention will become apparent from a consideration of the detailed description.
Not applicable.
The vinyl copolymer emulsion according to this invention is obtained by the emulsion polymerization of:
(A) 50-99.9 weight percent a vinyl monomer;
(B) 0.1-50 weight percent of an organosilicon compound bearing a radically polymerizable organic group, the compound having the formula 
in which X is a radically polymerizable organic group, R1 is a C1 to C10 alkyl group or a C6 to C12 aryl group, R2 is a C1 to C10 alkyl group, a is a number with an average value of 2-3; the sum of the amounts of components (A) and (B) being 100 weight percent; and
(C) a radically polymerizable surfactant used at 0.1-20 weight parts for each 100 weight parts of the total amount of components (A) and (B). The emulsion is useful as a paint and coating additive.
The vinyl monomer (A) should bear a radically polymerizable vinyl group, but the type and the properties of vinyl monomer (A) are not otherwise critical. When it is desired to obtain an improved water resistance for a film or coating, the main constituents of component (A) are preferably hydrophobic vinyl monomers and radically crosslinking vinyl monomer.
Hydrophobic vinyl monomers are exemplified by (i) alkyl (meth)acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, lauryl methacrylate, and stearyl methacrylate; (ii) aromatic group containing (meth)acrylates such as benzyl acrylate, phenoxyethyl acrylate, benzyl methacrylate, and phenoxyethyl methacrylate; (iii) vinyl esters of aliphatic acids such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl 2-ethylhexanoate, vinyl laurate, and vinyl stearate; (iv) aromatic vinyl monomers such as styrene and vinyltoluene; (v) diene monomers such as butadiene and isoprene; (vi) halogenated vinyl monomers such as vinyl chloride and vinylidene chloride; (vii) nitrile monomers such as acrylonitrile and methacrylonitrile; and (viii) diorganopolysiloxanes bearing a radically polymerizable functional group such as an acrylic, methacrylic, or styryl group, at one molecular chain terminal. Most preferred are alkyl (meth)acrylates and aromatic vinyl monomers such as styrene.
The radically crosslinking vinyl monomers are compounds containing at least two radically polymerizable organic groups in their molecule. These compounds are exemplified by (i) alkenyl (meth)acrylates such as allyl methacrylate and allyl acrylate; (ii) multifunctional (meth)acryloyl functional compounds such as trimethylolpropane triacrylate, pentaerythritol triacrylate, ethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane trioxyethylacrylate, tris(2-hydroxyethyl)isocyanurate diacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trioxyethylmethacrylate, tris(2-hydroxyethyl)isocyanurate dimethacrylate, and tris(2-hydroxyethyl)isocyanurate trimethacrylate; (iii) diacrylates and dimethacrylates of diols that are adducts of ethylene oxide or propylene oxide on bisphenol A, and diacrylates and dimethacrylates of diols that are adducts of ethylene oxide or propylene oxide on hydrogenated bisphenol A; (iv) methacryloxypropyl functional polydimethylsiloxanes; and (v) multifunctional vinyl monomers such as divinylbenzene, triethylene glycol divinyl ether, and styryl functional polydimethylsiloxanes. The radically crosslinking vinyl monomer is employed in the range of 0.1-10 weight percent of the overall vinyl monomer content, preferably in the range of 1-5 weight percent.
In addition to vinyl monomers such as described above, component (A) may contain other vinyl monomers that bear a reactive functional group and/or vinyl monomers bearing a property conferring functional group. Monomers of this type are exemplified by (i) hydroxyl functional vinyl monomers such as 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxybutyl methacrylate, and 2-hydroxypropyl methacrylate; (ii) epoxy functional vinyl monomers such as glycidyl acrylate, 3,4-epoxycyclohexylmethyl acrylate, glycidyl methacrylate, and 3,4-epoxycyclohexylmethyl methacrylate; (iii) amino functional vinyl monomers such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, and diethylaminoethyl methacrylate; (iv) amide functional vinyl monomers such as acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, isobutoxymethoxyacrylamide, N,N-dimethylacrylamide, methacrylamide, N-methylolmethacrylamide, N-methoxymethylmethacrylamide, isobutoxymethoxymethacrylamide, and N,N-dimethylmethacrylamide; (v) fluorinated vinyl monomers such as trifluoropropyl acrylate, perfluorobutylethyl acrylate, perfluorooctylethyl acrylate, trifluoropropyl methacrylate, perfluorobutylethyl methacrylate, and perfluorooctylethyl methacrylate; and (vi) ether linkage containing vinyl monomers such as tetrahydrofurfuryl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, polyethylene glycol acrylate, polypropylene glycol monoacrylate, hydroxybutyl vinyl ether, cetyl vinyl ether, 2-ethylhexyl vinyl ether, tetrahydrofurfuryl methacrylate, butoxyethyl methacrylate, ethoxydiethylene glycol methacrylate, polyethylene glycol methacrylate, and polypropylene glycol monomethacrylate.
Some examples of additional vinyl monomers that bear a reactive functional group and/or vinyl monomers that bear a property conferring functional group include alkoxysilanes containing a radically polymerizable unsaturated group such as CH2xe2x95x90CHCOOC3H6Si(OCH3)3, CH2xe2x95x90C(CH3)COOC3H6Si(OCH3)3, CH2xe2x95x90C(CH3)COOC3H6Si(CH3)(OCH3)2, CH2xe2x95x90C(CH3)COOC3H6Si(CH3)2OCH3, CH2xe2x95x90C(CH3)COOC2H4OC3H6Si(OCH3)3, CH2xe2x95x90C(CH3)COOC12H24Si(OCH3)3, CH2xe2x95x90CHOC3H6Si(CH3)(OC2H5)2, CH2xe2x95x90CHSi(OCH3)3, CH2xe2x95x90CHSi(OC2H5)3, and CH2xe2x95x90CHSi(C4H9)(OC4H9)2.
Further examples of vinyl monomers bearing a reactive functional group and/or vinyl monomers bearing a property-conferring functional group include dibutyl fumarate; maleic anhydride; dodecylsuccinic anhydride; radically polymerizable unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid, as well as their salts, ammonium salts, and organic amine salts; radically polymerizable unsaturated monomers that contain a sulfonic acid residue such as styrene sulfonic acid as well as their alkali metal salts, ammonium salts, and organic amine salts; quaternary ammonium salts derived from (meth)acrylic acid such as 2-hydroxy-3-methacryloxypropyl trimethylammonium chloride; and methacrylate esters of alcohols that contain a tertiary amine group such as the diethylamine ester of methacrylic acid as well as the quaternary ammonium salt thereof.
When a vinyl monomer is used which bears a reactive functional group such as amino, epoxy, carboxyl, hydroxyl, blocked isocyanate, or silyl group such as alkoxysilyl or acetoxysilyl, the film or coating of the vinyl copolymer emulsion or the paint or coating composition containing the emulsion can undergo crosslinking. This feature provides additional enhancements in water resistance of paints or coatings. The crosslinking can be of a self crosslinking type or it may be induced by using a crosslinker such as melamine, a multifunctional epoxy compound or multifunctional isocyanate compound. Crosslinking catalysts can also be used.
Component (B) is an organosilicon compound bearing a radically polymerizable organic group. It has the formula 
The X group in formula (1) represents a radically polymerizable organic group and is exemplified by (i) acryl and methacryl functional organic groups with the formulas 
(ii) styryl functional organic groups with the formula 
and (iii) C2 to C10 alkenyl groups.
R4 and R6 in the above formulas each denote hydrogen or methyl; R5 and R8 each denote a C1 to C10 alkylene group; R7 denotes a C1 to C10 alkyl group; b is zero or an integer with a value of 1 to 4; and c is 0 or 1. The radically polymerizable organic group X is exemplified by acryloxymethyl, 3-acryloxypropyl, methacryloxymethyl, 3-methacryloxypropyl, 4-vinylphenyl, 3-vinylphenyl, 4-(2-propenyl)phenyl, 3-(2-propenyl)phenyl, 2-(4-vinylphenyl)ethyl, 2-(3-vinylphenyl)ethyl, vinyl, allyl, methallyl, and 5-hexenyl.
R1 in formula (1) is a C1 to C10 alkyl group or a C6 to C12 aryl group. The alkyl group is exemplified by methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, cyclopentyl, and cyclohexyl. The aryl group is exemplified by phenyl and naphthyl. Methyl and phenyl groups are preferred for R1 particularly methyl. R2 in formula (1) is a C1 to C10 alkyl group exemplified by methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, cyclopentyl, and cyclohexyl, with methyl being the preferred group.
Component (A) is used in an amount corresponding to 50-99.9 weight percent of the total amount of components (A) and (B), preferably 75-99.9 weight percent of the total amount of components (A) and (B).
Component (B) is exemplified by compounds with the following average formulas in which Me represents the methyl group: 
Component (B) can be synthesized by methods known in the art. Component (B) is employed in a quantity corresponding to 0.1-50 weight percent of the total amount of components (A) and (B), preferably 0.1-25 weight percent of the total amount of components (A) and (B). The beneficial features of component (B) do not appear when component (B) is used at less than 0.1 weight percent, while film strength and compatibility are reduced when it is used at more than 50 weight percent.
The radically polymerizable surfactant component (C) should exhibit surfactancy, and it should be capable of undergoing radical polymerization. Component (C) may be an anionic, nonionic, or cationic surfactant. Below are shown various structures representative of component (C). In these structures, R is hydrogen or a methyl group, R1 is hydrogen or a C1-20 alkyl group, R2 is an alkylene radical, AO is an alkylene oxide, M is an alkali metal, X is a halogen atom, EO is ethylene oxide, PO is propylene oxide, and x is 1-50.
Anionic surfactants representative of component (C) are exemplified by compounds with the following structures.
Acrylic Types of Anionic Surfactant (C) 
Allylic Types of Anionic Surfactant (C) 
Maleic Acid Types of Anionic Surfactant (C) 
Itaconic Acid Types of Anionic Surfactant (C) 
The nonionic types of radically polymerizable surfactant (C) can be exemplified by the following compounds.
Acrylic Types of Nonionic Surfactant (C) 
Allylic Types of Nonionic Surfactant (C) 
Maleic Acid Types of Nonionic Surfactant (C) 
Itaconic Acid Types of Nonionic Surfactant (C) 
The cationic types of radically polymerizable surfactant (C) can be exemplified by the following compounds.
Acrylic Types of Cationic Surfactant (C) 
Allylic Types of Cationic Surfactant (C) 
The following surfactants are most preferred. 
Component (C) can be a single surfactant or combination of two or more surfactants. It is used in amounts of 0.1-20 weight parts per 100 weight parts of the total amount of components (A) and (B). When it is desired to obtain better water resistance, component (C) should be present in amounts of 0.1-3 weight parts per 100 weight parts of the total amount of components (A) and (B).
The vinyl copolymer emulsion according to this invention is obtained by the emulsion polymerization of components (A), (B), and (C). A radical polymerization initiator can be used in the emulsion polymerization process to shorten reaction time. Some suitable radical polymerization initiators include inorganic peroxides such as potassium persulfate, sodium persulfate, and ammonium persulfate; organoperoxides such as tert-butyl peroxymaleic acid, succinic acid peroxide, and tert-butyl hydroperoxide; water soluble azo-type radical initiators such as 2,2xe2x80x2-azobis{2-(N-benzylamidino)propane} hydrochloride, 2,2xe2x80x2-azobis{2-(N-2-hydroxyethylamidino)propane} hydrochloride, and 2,2xe2x80x2-azobis(2-methyl-N-hydroxyethyl)propionamide; oil soluble azo-type radical initiators such as 2,2xe2x80x2-azobisisobutyronitrile, 2,2xe2x80x2-azobis-2,4-dimethylvaleronitrile, 1-azobis-1-cyclohexanecarbonitrile, dimethyl 2,2xe2x80x2-azobisisobutyrate, and 4,4xe2x80x2-azobis-4-cyanovaleric acid; and oil soluble peroxides such as lauroyl peroxide, benzoyl peroxide, dicumyl peroxide, cyclohexanone peroxide, di-n-propyl peroxydicarbonate, and tert-butyl peroxypivalate. The radical initiator is used in amounts of 0.01-20 weight parts, preferably 0.1-10 weight parts, in each case per 100 weight parts of the total amount of components (A) and (B).
The particular sequence of conducting emulsion polymerization is not critical, however, the following methods can be used as being representative of the process. In one method, the mixture of components (A), (B), and (C) is first emulsified and dispersed in an aqueous medium, the radical initiator is added to the emulsion, and polymerization is carried out by heating. In another method, components (B) and (C) are first emulsified and dispersed in an aqueous medium, component (A) is added to the emulsion, followed by addition of the radical initiator, and polymerization is thereafter carried out by heating. In either case, the emulsified dispersion can be prepared using known emulsification devices such as a colloid mill or an homogenizer. Polymerization should be carried out for 2-8 hours at 50-90xc2x0 C. It can be carried out while adding the emulsified dispersion dropwise into the water at 50-90xc2x0 C., or after introducing the entire emulsified dispersion in one batch into water at 50-90xc2x0 C.
If desired, a chain transfer agent for use in radical polymerization may be included with components (A), (B), and (C). Some appropriate chain transfer agents are exemplified by mercapto compounds such as 2-mercaptoethanol, butyl mercaptan, n-dodecyl mercaptan, 3-mercaptopropyltrimethoxysilane, and mercaptopropyl functional polydimethylsiloxanes; halogen compounds such as methylene chloride, chloroform, carbon tetrachloride, butyl bromide, and 3-chloropropyltrimethoxysilane; and the alpha-methylstyrene dimer.
The post polymerization particle size of the copolymer emulsion is not critical. However, from the standpoint of storage stability and prevention of appearance of aggregates, it should be no greater than 1.0 xcexcm, preferably no greater than 0.5 xcexcm, and most preferably no greater than 0.3 xcexcm. A thickener can also be added and/or the specific gravity can be adjusted, when the particle size is 1.0 xcexcm or above. Similarly, the solids content of the composition can range from 10-80 weight percent, preferably 15-60 weight percent.
Other additives such as colorants, stabilizers, fats, oils, waxes, and fillers, can be included. The composition may contain a curing catalyst for alkoxysilyl or silanol groups within a range that would not impair stability of the composition. Some representative curing catalysts are organometallic salts, metal alkoxides, metal chelates, organic amines, and quaternary ammonium salts. The curing catalyst will function to improve adherence of the composition to substrates by accelerating the reaction between the composition of the invention and the surface of various substrates.
One benefit of the vinyl copolymer emulsion according to this invention is the low content of unreacted silicone in the vinyl copolymer produced by emulsion polymerization. This is because there exists high reactivity between the vinyl monomer and the radically polymerizable organosilicon compound. As a consequence, the films, coatings, and cured products obtained from the vinyl copolymer emulsion possess excellent compatibility with other materials such as organic resins, an excellent adherence for various substrates, resistance to slippage or sliding due to improved friction properties, and excellent printability and writability. Such films, coatings, and cured products also exhibit excellent weathering resistance, UV resistance, gloss retention, waterproofness, icing resistance, and acid resistance. In addition, the use of a radically polymerizable surfactant results in very good water resistance, while storage stability is also excellent. Since the vinyl copolymer emulsion is a waterborne system, it is very safe and imposes little environmental burden in terms of air pollution, for example.
Such features render compositions according to the invention useful as a resin or an additive for application in paints and coatings. It can also constitute the main ingredient or additive for waxes, paper processing agents, fiber treatment agents, film processing agents, cosmetics, civil engineering resins, adhesives, and pressure-sensitive adhesives. Films or coatings of the compositions can be formed by coating the composition on any of a number of various substrates and heating it for 5 minutes to 10 hours at 30-90xc2x0 C., or by maintaining it at room temperature for 1 hour to 5 days. The film or coating thickness will generally be from 0.1-100 xcexcm.